Conventionally, a system is known in which a transmission device is connected to a system bus of a controller and has the function to process communication commands from the controller. In such a system, when the operation of the transmission device and the task of the controller are asynchronously carried out, there may be an overlap in their individual timings at which the transmission device and the controller use shared system resources (such as a system bus and shared memories). Such an overlap may cause a delay in the execution of the task by the controller. As a general countermeasure thereto, for example, the transmission device sets a waiting time at key points of the operation which occupies the shared system resources over a long period of time and temporarily yields the shared system resources to the controller during the waiting time.
However, even if the above countermeasure is taken, a delay may still occur in the task execution by the controller during a time taken for yielding the shared system resources.
It is an object of the present invention to provide a transmission device, a controller, and a system including the transmission device and the controller that enable the controller to execute a task without a delay, unaffected by the operation by the transmission device.